Saline-alkali soils seriously restrict agricultural productivity, reduce carbon (C) sequestration and increase global warming potential (GWP) of farmland systems. Straw return is usually used to improve soil physicochemical properties, increase soil organic carbon (SOC) and crop yield in saline-alkali arid farmland. The performance of straw return is influenced by varieties of factors including incorporation mode, soil type, crop and climate. Therefore, from 2017 to 2019, a three-year short-term study was conducted to investigate the impact of different straw return modes on soil greenhouse gas (GHG) emissions, net ecosystem C budget (NECB), net global warming potential (NGWP) and C footprint in a saline-alkali farmland under arid conditions. Four straw return modes, namely straw return with rotary tillage, straw return with plowing, and straw-derived biochar treatment and a control without straw return, were conducted in saline-alkali arid farmland. Results indicated that compared with the control, straw return with rotary tillage increased direct GHG emissions (soil borne CO and NO emissions), while straw-derived biochar decreased direct GHG emissions. Straw return with plowing had no significant impact on direct GHG emissions. Straw return with plowing, straw return with rotary tillage, and straw-derived biochar significantly increased indirect CO emissions due to more consumption of energy, fossil fuels and diesel than the control. For C sequestration, straw return significantly increased crop C fixation and soil C sequestration compared with the control. The C sequestration in straw-derived biochar treatment was significantly higher than that of the return with rotary tillage and plowing treatments, thus achieving the highest NECB and the lowest NGWP and yield-scaled C footprint. Compared to the control, straw-derived biochar mode increased NECB by 2618.4−11379.4 kg ha, and decreased NGWP and yield-scaled C footprint by 12660.4−43431.9 kg ha and 0.03−1.9 kg kg, respectively. Overall, the short-term results suggested that crop C fixation and soil C sequestration are crucial determinants of the NECB and C footprint, respectively. Return in the form of biochar could be recommended as an appropriate straw return practice for enhancing C sequestration and mitigating the GWP of the saline-alkali farmland.

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不同秸秆还田模式对盐碱干旱农田生态系统净碳预算和碳足迹的影响对比

盐碱土壤严重限制了农业生产力，减少了农田系统的碳固存并增加了全球变暖潜势（GWP）。秸秆还田通常用于改善盐碱干旱农田的土壤理化性质，增加土壤有机碳（SOC）和作物产量。秸秆还田效果受秸秆还田方式、土壤类型、作物和气候等多种因素的影响。因此，2017年至2019年开展了为期三年的短期研究，探讨不同秸秆还田模式对土壤温室气体（GHG）排放、净生态系统碳预算（NECB）、净全球变暖潜势（NGWP）的影响干旱条件下盐碱农田的碳足迹和碳足迹。在盐碱干旱农田实施秸秆旋耕还田、秸秆翻耕还田、秸秆生物炭处理和秸秆不还田对照4种秸秆还田模式。结果表明，与对照相比，秸秆还田旋耕增加了直接温室气体排放（土壤中的二氧化碳和氧化氮排放），而秸秆生物炭则减少了直接温室气体排放。秸秆还田耕作对直接温室气体排放没有显着影响。耕作秸秆还田、旋耕秸秆还田和秸秆生物炭由于比对照消耗更多的能源、化石燃料和柴油，显着增加了间接二氧化碳排放。对于碳固存，与对照相比，秸秆还田显着增加了作物碳固定和土壤碳固存。秸秆生物炭处理中的碳封存显着高​​于旋耕和犁耕处理的还田，从而实现了最高的 NECB 和最低的 NGWP 和产量规模碳足迹。与对照相比，秸秆生物炭模式使 NECB 增加了 2618.4−11379.4 kg·ha，NGWP 和产量规模碳足迹分别减少了 12660.4−43431.9 kg·ha 和 0.03−1.9 kg·kg。总体而言，短期结果表明作物碳固定和土壤碳固存分别是 NECB 和碳足迹的关键决定因素。建议以生物炭形式返还作为一种适当的秸秆返还做法，以增强碳封存并减轻盐碱农田的全球升温潜能值。